Polylactic acid base polymer composition, molding thereof and film

ABSTRACT

Poly(lactic acid) polymer compositions each contain an appropriate poly(lactic acid) polymer and a suitable plasticizer having a polyether and/or polyester segment in combination. The compositions exhibit satisfactory flexibility and show very small amount of the evaporation, migration and extraction (bleedout) of the plasticizer and losing transparency upon heating. The poly(lactic acid) polymer compositions are useful as formed plastics such as films.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.10/517,999, filed Jan. 11, 2005, which is a §371 of InternationalApplication No. PCT/JP2003/007808, with an international filing date ofJun. 19, 2003 (WO 2004/000939 A1, published Dec. 31, 2003), which isbased on Japanese Patent Application No. 2002-179806, filed Jun. 20,2002.

TECHNICAL FIELD

This disclosure relates to a poly(lactic acid) polymer composition,formed plastics thereof and a film. More specifically, it relates to apoly(lactic acid) polymer composition which exhibits flexibility by theaction of a plasticizer, is free from problems such as evaporation,migration and extraction (bleedout) of the plasticizer and/or losingtransparency upon heating and has excellent durability in use. It alsorelates to formed plastics thereof and a film.

BACKGROUND

Plastic wastes have been disposed typically by incineration orlandfilling. However, formation and discharge of harmful by-productsproduced as a result of incineration, reduction of landfill space andenvironmental pollution caused by unauthorized dumping have becomesignificant. With an increasing public concern on disposal of plasticwastes, research and development on biodegradable plastics such asaliphatic polyesters have been increasingly carried out. Suchbiodegradable plastics are decomposed by the action enzymes ormicroorganisms. Among the biodegradable aliphatic polyesters,poly(lactic acid)s have been aggressively investigated and developed.

The poly(lactic acid)s are polymers produced by preparing lactic acidtypically from a starch derived from corns or potatoes and subjectinglactic acid to chemical synthesis. The poly(lactic acid)s exhibitsuperior mechanical properties, heat resistance and transparency amongaliphatic polyesters. Research and development to provide formedplastics of poly(lactic acid)s, such as films, sheets, tapes, fibers,ropes, nonwoven fabrics and packages, have been increasingly carriedout. The poly(lactic acid)s as intact, however, have insufficientflexibility, and plasticizers are used to increase the flexibility ofpoly(lactic acid)s for use as, for example, packaging wrap films,stretch films and agricultural mulch films.

Japanese Unexamined Patent Application Publication No. 4-335060discloses a technique of using a plasticizer such as a phthalic esterwhich is generally used in vinyl chloride polymers. When a regularplasticizer such as a phthalic ester is added to give flexibility to apoly(lactic acid), the resulting formed plastics exhibits flexibilityimmediately after addition. However, if the formed plastics are left innormal atmosphere (atmosphere of the air) particularly at hightemperatures over a long time, the formed plastics exhibits remarkablyreduced flexibility and deteriorated transparency because theplasticizer in the formed plastics evaporates and bleeds out. Inaddition, when a regular plasticizer is added to give flexibility to apoly(lactic acid), the formed plastics exhibits remarkably reducedflexibility and decreased transparency in water, particularly in hotwater, because the plasticizer is extracted.

U.S. Pat. No. 5,180,765 and No. 5,076,983, and Japanese UnexaminedPatent Application Publication No. 6-306264 each disclose a technique ofusing lactic acid, a linear lactic acid oligomer or a cyclic lactic acidoligomer as a plasticizer. A poly(lactic acid) containing a considerableamount of lactic acid, a linear lactic acid oligomer or a cyclic lacticacid oligomer, however, exhibits poor thermal stability upon forming andis easily hydrolyzed under regular conditions for use. Formed plasticssuch as a film prepared from such a composition exhibits decreasedstrength in a relatively short time and is significantly insufficient inpractical utility as formed plastics.

Japanese Unexamined Patent Application Publication No. 8-199052discloses a technique on a composition including a poly(lacticacid)/poly(alkylene ether) copolymer, and a plasticizer mainlycomprising a poly(alkylene ether). According to this technique, however,the evaporation, migration and extraction (bleedout) of the plasticizerare not sufficiently controlled, although the composition exhibitsflexibility at practical level.

Japanese Unexamined Patent Application Publication No. 8-253665discloses a composition containing a polymer mainly comprising lacticacid, and a block copolymer between a poly(alkylene ether) and apoly(lactic acid). This technique is achieved in order to impartantistatic property, and the block copolymer containing the poly(lacticacid) component is added as an antistatic agent. The publicationindicates that the poly(lactic acid) component serves to increasechemical affinity of the block copolymer for a base material (matrix) tothereby make the block copolymer finely dispersed. The publication,however, gives neither indication on the other actions of thepoly(lactic acid) component nor concrete suggestion on the molecularweight thereof. We have double-checked the descriptions of JapaneseUnexamined Patent Application Publication No. 8-253665 from theviewpoints of the flexibility of the composition, and control(prevention) of the evaporation, migration and extraction (bleedout) ofthe additive (plasticizer) and losing transparency upon heating asformed plastics. But we have found that these properties areinsufficient.

As is described above, attempts have been made to give the flexibilityto a poly(lactic acid) by adding a plasticizer. No technique, however,has been achieved to impart sufficient flexibility to a poly(lacticacid) and to control the evaporation, migration and extraction(bleedout) of the plasticizer and losing transparency upon heating inuse as formed plastics.

Attempts have also been made to provide techniques for impartingtypically flexibility to a poly(lactic acid) film having transparencyand heat resistance to thereby use it as a trash bag or agriculturalfilm, and techniques for imparting typically flexibility and adhesion toa poly(lactic acid) film to thereby use it as a packaging wrap film.

For use as packaging wrap films, Japanese Unexamined Patent ApplicationPublication No. 2000-26623, for example, discloses a stretched filmcomprising a composition containing a liquid additive and a resin mainlycontaining an aliphatic lactic acid-based polyester. We have made anactual attempt to form a stretched film in accordance with the examplesdescribed in Japanese Unexamined Patent Publication No. 2000-26623. Theresulting stretched film exhibits flexibility, heat-resistance andtransparence at certain levels as a packaging wrap film for foodpackaging only immediately after film formation. The film, however,loses its flexibility and adhesion and lacks practical utility after useor storage at room temperature for about several weeks, since the liquidadditive readily evaporates, bleeds out and attaches to a substance tobe wrapped.

As is described above, no packaging wrap film comprising a poly(lacticacid) polymer composition being excellent in flexibility, transparency,heat resistance and adhesion has yet been realized.

SUMMARY

We provide a first embodiment including a poly(lactic acid) polymercomposition comprising a poly(lactic acid) polymer exhibitingcrystallinity and a plasticizer, in which the plasticizer has at leastone poly(lactic acid) segment having a molecular weight of 1200 or moreper molecule and comprises a polyether and/or polyester segment.

We provide a second embodiment including a poly(lactic acid) polymercomposition comprising a poly(lactic acid) polymer exhibitingcrystallinity, a poly(lactic acid) polymer exhibiting no crystallinity,and a plasticizer, in which the plasticizer comprises a polyether and/orpolyester segment and has no poly(lactic acid) segment having amolecular weight of 1200 or more.

We provide a third embodiment including a poly(lactic acid) polymercomposition comprising a poly(lactic acid) polymer exhibitingcrystallinity and having a melting point lower than 145° C., and aplasticizer, in which the plasticizer comprises a polyether and/orpolyester segment and has no poly(lactic acid) segment having amolecular weight of 1200 or more.

In addition, we provide a fourth embodiment including a poly(lacticacid) polymer composition comprising a poly(lactic acid) polymerexhibiting no crystallinity, and a plasticizer, the compositioncontaining no poly(lactic acid) polymer exhibiting crystallinity, inwhich the plasticizer comprises a polyether and/or polyester segment.

The poly(lactic acid) polymer compositions have sufficient flexibilityand show very small amount of the evaporation, migration and extraction(bleedout) of plasticizers and losing transparency upon heating in useas formed plastics.

DETAILED DESCRIPTION

Poly(lactic acid) polymers for use in the poly(lactic acid) polymercompositions of the first, second, third and fourth embodiments arepoly(lactic acid) polymers each mainly comprising L-lactic acid and/orD-lactic acid and containing components derived from lactic acid in anamount of 70 percent by weight or more of the total of the polymer.Homopoly(lactic acid)s substantially comprising L-lactic acid and/orD-lactic acid are preferably used as the poly(lactic acid) polymers.

In general, such homopoly(lactic acid)s each have an elevating meltingpoint and increasing crystallinity with an increasing optical purity.The melting point and crystallinity of a poly(lactic acid) are affectedby its molecular weight and a catalyst used in polymerization. Ahomopoly(lactic acid) having an optical purity of 98% or more, forexample, generally has a melting point of about 170° C. and exhibitsrelatively high crystallinity. The melting point and crystallinitydecrease with a decreasing optical purity. A homopoly(lactic acid)having an optical purity of 88%, for example, has a melting point ofabout 145° C., and a homopoly(lactic acid) having an optical purity of75% has a melting point of about 120° C. A homopoly(lactic acid) havingan optical purity lower than 70% does not have a clear melting point andis amorphous.

The phrase “a poly(lactic acid) polymer exhibits crystallinity” meansthat heat of fusion of crystal derived from a poly(lactic acid)component is observed when the poly(lactic acid) polymer is sufficientlycrystallized under heating and is then subjected to measurement using adifferential scanning calorimeter (DSC) in an appropriate temperaturerange.

A lactide process and a direct polymerization process are known asprocesses for producing a poly(lactic acid). According to the lactideprocess, a poly(lactic acid) is produced in two steps, i.e., bypreparing a lactide, a cyclic dimer, from L-lactic acid, D-lactic acidor DL-lactic acid (racemate) as a raw material, and subjecting thelactide to ring-opening polymerization. According to the directpolymerization process, a poly(lactic acid) is produced in one step ofsubjecting the raw material to direct dehydration condensation in asolvent. The homopoly(lactic acid) can be prepared by any of theproduction processes. A homopoly(lactic acid) prepared by the directpolymerization process is substantially free from problems caused by thecyclic dimer and is suitable from the viewpoints of formability andfilm-forming property. In a polymer prepared by the lactide process, thecyclic dimer contained therein evaporates during forming and causesdeposition on a cast drum upon melting film formation or decreasedsmoothness of the surface of the resulting film. The content of thecyclic dimer in the polymer before forming or melting film formation ispreferably controlled to 0.3 percent by weight or less.

The weight-average molecular weight of the poly(lactic acid) polymer isgenerally at least 50000, preferably 80000 to 300000, and morepreferably 100000 to 200000. When the average molecular weight is set at50000 or more, the resulting formed plastics such as a film exhibitssatisfactory physical properties in strength.

The poly(lactic acid) polymer may be a lactic acid copolymer prepared bycopolymerizing another monomer component capable of forming an ester, inaddition to L-lactic acid and/or D-lactic acid. Examples of suchcopolymerizable monomer component are hydroxycarboxylic acids such asglycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid,4-hydroxyvaleric acid and 6-hydroxycaproic acid; compounds each havingplural hydroxyl groups in the molecule, and derivatives thereof, such asethylene glycol, propylene glycol, butanediol, neopentyl glycol,poly(ethylene glycol)s, glycerol and pentaerythritol; compounds eachhaving plural carboxylic acids in the molecule and derivatives thereof,such as succinic acid, adipic acid, sebacic acid, fumaric acid,terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid,5-sodiosulfoisophthalic acid and 5-tetrabutylphosphoniumsulfoisophthalate. The copolymeric component of the poly(lactic acid)polymer is preferably selected from among biodegradable components.

The plasticizers for use in the poly(lactic acid) polymer compositionsof the first, second, third and fourth embodiments each comprise apolyether and/or polyester segment.

Such compounds comprising a polyether and/or polyester segment haverelatively high affinity for a poly(lactic acid) and highly efficientlyserve to plasticize the poly(lactic acid). By introducing a polyetherand/or polyester segment into the plasticizer, the flexibility can beimparted to the poly(lactic acid).

The plasticizers for use in the poly(lactic acid) polymer compositionsof the first, second, third and fourth embodiments preferably comprisepolyester segments, of which poly(alkylene ether) segments are morepreferred, of which poly(ethylene glycol) segments are typicallypreferred.

When the plasticizers have segments comprising a poly(alkylene ether)such as a poly(ethylene glycol), poly(propylene glycol) or poly(ethyleneglycol)/poly(propylene glycol) copolymer, particularly poly(ethyleneglycol), they have especially high affinity for a poly(lactic acid)polymer and highly efficiently serve to plasticize the poly(lactic acid)polymer. Thus, a poly(lactic acid) polymer composition having a desiredflexibility can be prepared by the addition of the plasticizer in asmall amount.

When the plasticizers have the segment comprising a poly(alkyleneether), especially poly(ethylene glycol), the average molecular weightof the segment is preferably 1000 or more, and more preferably 2000 ormore. By setting the average molecular weight at 1000 or more, theevaporation of the plasticizer can be highly prevented. The averagemolecular weight is generally at highest 500,000 or less and ispreferably 20000 or less. When an average molecular weight is 50000 orless, the affinity for the poly(lactic acid) polymer increases and theplasticizing efficiency remarkably increases.

When the plasticizer contains a segment comprising a poly(alkyleneether), an antioxidant such as a hindered phenol or hindered amineantioxidant and/or a thermal stabilizer such as a phosphorus thermalstabilizer as described later is preferably used, since thepoly(alkylene ether) segment is susceptible to oxidation and thermaldecomposition upon heating typically in forming.

The poly(lactic acid) polymer composition of the first embodiment willbe described below.

The poly(lactic acid) polymer composition of the first embodiment is apoly(lactic acid) polymer composition comprising a poly(lactic acid)polymer exhibiting crystallinity and a plasticizer, in which theplasticizer has at least one poly(lactic acid) segment having amolecular weight of 1200 or more per molecule and comprises a polyetherand/or polyester segment.

When a homopoly(lactic acid) is used in the poly(lactic acid) polymercomposition of the first embodiment, the homopoly(lactic acid) may havean optical purity of 75% or more. If the poly(lactic acid) polymer foruse in the poly(lactic acid) polymer composition of the first embodimentexhibits no crystallinity, the evaporation, migration and extraction(bleedout) of the plasticizer is not sufficiently controlled.

The poly(lactic acid) polymer composition of the first embodimentcomprises a plasticizer that comprises a polyether and/or polyestersegment and has, per molecule, at least one poly(lactic acid) segmenthaving a molecular weight of 1200 or more.

The poly(lactic acid) segment in the plasticizer is preferably 1500 ormore. By setting the poly(lactic acid) segment of the plasticizer at1500 or more, the poly(lactic acid) segment in the plasticizer isincorporated into crystals comprising the matrix poly(lactic acid)polymer and serves to anchor the molecule of the plasticizer to thematrix. Thus, the evaporation, migration and extraction (bleedout) ofthe plasticizer can be prevented at high levels.

A poly(lactic acid) segment having a molecular weight of 10,000 or morein the plasticizer may decrease the plasticizing efficiency of theplasticizer, which in turn prevents the impartment of-practicalflexibility.

The plasticizer for use in the poly(lactic acid) polymer composition ofthe first embodiment comprises a poly(lactic acid) segment exhibitingcrystallinity. The heat of fusion of crystal (ΔH_(po)) derived from thepoly(lactic acid) segment of the plasticizer as determined bymeasurement using a DSC is preferably 3.0 J/g or more, more preferably10.0 J/g or more, and further preferably 20.0 J/g or more. The measuringprocess of ΔH_(po) is described in the examples.

In the plasticizer for use in the poly(lactic acid) polymer composition,the compositional ratio of the L-lactic acid component to the D-lacticacid component constituting the poly(lactic acid) segment is preferably100:0 to 95:5 or 5:95 to 0:100. The plasticizer having such acompositional ratio can yield a poly(lactic acid) polymer compositionthat is specifically free from the evaporation, migration and extraction(bleedout) of the plasticizer.

The poly(lactic acid) polymer composition of the first embodimentpreferably further comprises a poly(lactic acid) polymer exhibiting nocrystallinity. By incorporating a poly(lactic acid) polymer exhibitingno crystallinity, losing transparency upon heating can be controlled ata higher level, in addition to the control of the evaporation, migrationand extraction (bleedout) of the plasticizer.

The proportion of the poly(lactic acid) polymer exhibiting nocrystallinity may be set according to the application.

In contrast to regular polyesters such as poly(ethylene terephthalate)s,poly(lactic acid) polymers hardly undergo transesterification when twoor more different poly(lactic acid) polymers having, for example,different compositions, melting points or crystallinity are dry-blendedto form a mixture and the mixture is subjected to melt extrusionaccording to a conventional procedure. Thus, the poly(lactic acid)polymer composition of the first embodiment preferably comprises apoly(lactic acid) having an optical purity of 95% or more as at leastone of poly(lactic acid) polymers to be used and further comprises anamorphous poly(lactic acid) polymer exhibiting no crystallinity. Thissufficiently controls the evaporation, migration and extraction(bleedout) of the plasticizer and losing transparency upon heating andyields a poly(lactic acid) polymer composition having high heatresistance.

The poly(lactic acid) polymer composition of the first embodiment can beformed into a formed plastics. The poly(lactic acid) polymer compositionof the first embodiment is preferably stretched 1.1 times or more in atleast one axial direction to form a formed plastics.

Stretching the formed plastics orients and crystallizes the matrixpoly(lactic acid) polymer and advances the incorporation of thepoly(lactic acid) segment of the plasticizer into the crystals. Thus,the evaporation, migration and extraction (bleedout) of the plasticizercan further be prevented.

Stretching the formed plastics also improves physical properties instrength of the formed plastics due to orientation and crystallizationand thereby yields formed plastics having both flexibility and strength.

A nucleating agent for accelerating crystallization may be used incombination when the poly(lactic acid) polymer composition of the firstembodiment is formed into a formed plastics. This may accelerate theincorporation of the poly(lactic acid) segment of the plasticizer intothe crystals comprising the matrix poly(lactic acid) polymer to therebyanchor the molecule of the plasticizer to the matrix, which in turn mayfurther control the evaporation, migration and extraction (bleedout) ofthe plasticizer. Examples of the nucleating agent are inorganicnucleating agents such as talc and organic nucleating agents such aserucamide.

The poly(lactic acid) polymer composition of the first embodimentcomprises a plasticizer having at least one poly(lactic acid) segmenthaving a molecular weight of 1200 or more per molecule and comprising apolyether and/or polyester segment.

The plasticizer having at least one poly(lactic acid) segment having amolecular weight of 1200 or more per molecule and comprising a polyetherand/or polyester-segment can be, for example, prepared by preparing apoly(lactic acid) oligomer having a molecular weight of 1200 or moreaccording to a conventional procedure such as lactide ring-opening orlactic acid polycondensation, and reacting the resulting poly(lacticacid) oligomer with an appropriate amount of a compound having apolyether and/or polyester segment and serving as a main component ofthe plasticizer. The plasticizer may be prepared as an addition polymerby ring-opening polymerization of lactide using, as a polymerizationinitiator, the compound serving as a main component of the plasticizeror by dehydration polycondensation of lactic acid using, as apolymerization initiator, the compound serving as a main component ofthe plasticizer. The plasticizer may also be prepared by allowing abifunctional compound such as a dicarboxylic anhydride compound or adiisocyanate compound to act as a linking agent upon the poly(lacticacid) oligomer having a molecular weight of 1200 or more with thecompound serving as a main component of the plasticizer in coexistenceby means of a treatment such as kneading under heating to therebychemically bond the two components.

More concrete examples of the plasticizer that has at least onepoly(lactic acid) segment having a molecular weight of 1200 or more permolecule and comprises a polyether and/or polyester segment will beillustrated below.

Initially, a poly(ethylene glycol) (PEG) having terminal hydroxyl groupsat both ends is prepared. The average molecular weight (M_(PEG)) of thepoly(ethylene glycol) (PEG) having terminal hydroxyl groups at both endsis generally determined by calculation from a hydroxyl value which isdetermined typically according to a neutralization process in the caseof a commercially available product. A total of w_(A) parts by weight oflactide is added to w_(B) parts by weight of the poly(ethylene glycol)(PEG) having terminal hydroxyl groups at both ends, and the lactide issubjected sufficiently to ring-opening addition polymerization to theterminal hydroxyl groups at both ends of PEG. This yields a blockcopolymer substantially having a PLA (A)-PEG (B)-PLA (A) configuration.This reaction may be carried out in the coexistence of a catalyst suchas tin octylate according to necessity.

The number-average molecular weight of one poly(lactic acid) segment ofthe plasticizer comprising the block copolymer can be-substantiallydetermined as (½)×(w_(A)/w_(B))×M_(PEG). The amount (weight percentage)of the poly(lactic acid) segment component can be substantiallydetermined as 100×w_(A)/(w_(A)+w_(B)) percent of the total plasticizer.The weight percentage of the plasticizing component other than thepoly(lactic acid) segment component can be substantially determined as100×w_(B)/(w_(A)+w_(B)) percent of the total plasticizer.

When unreacted materials such as unreacted PEG and a PEG containing aterminal poly(lactic acid) segment having a molecular weight of lessthan 1200, by-products such as lactide oligomers, or impurities need tobe removed, following purification processes can be applied.

The synthesized plasticizer is uniformly dissolved in an appropriategood solvent such as chloroform, and an appropriate poor solvent such asa mixture of water and methanol or diethyl ether is added dropwisethereto.

Alternatively, a solution of the plasticizer in a good solvent is addedto large excess of a poor solvent to form a precipitate, the precipitateis separated typically by centrifugation or filtration, and the solventis evaporated.

The purification process is not specifically limited to the aboveexamples, and any of the above procedures may be repeated plural timesaccording to necessity.

When the plasticizer comprising the PLA (A)-PEG (B)-PLA (A) blockcopolymer is prepared by the above process, the molecular weight of onepoly(lactic acid) segment in the plasticizer can be determined in thefollowing manner.

The plasticizer is dissolved in deuterium chloroform, and the solutionis subjected to 1H-NMR measurement. The molecular weight is determinedby calculation according to the following equation based on theresulting chart:Molecular weight=(½)×(I _(PLA)×72)/(I _(PEG)×44/4)×M _(PEG)wherein I_(PEG) is the integrated intensity of signals derived fromhydrogen of the methylene group of the principal chain of PEG; andI_(PLA) is the integrated intensity of signals derived from hydrogen ofthe methine group of the principal chain of PLA.

When the plasticizer is prepared under such conditions that the lactidereacts satisfactorily and substantially all the lactide undergoesring-opening addition to the terminals of PEG, the molecular weight isoften preferably determined based on the chart obtained by 1H-NMRmeasurement.

The poly(lactic acid) polymer composition of the first embodiment hassufficient flexibility by using, as the plasticizer, a block copolymerhaving a PLA (A)-PEG (B)-PLA (A) configuration and having at least onepoly(lactic acid) segment having a molecular weight of 1200 or more permolecule. The poly(lactic acid) polymer composition of the firstembodiment yields formed plastics, such as a film, which shows verysmall amount of the evaporation, migration and extraction (bleedout) ofthe plasticizer.

The poly(lactic acid) polymer composition of the first embodiment hasexcellent durability in use and show very small amount of theevaporation, migration and extraction (bleedout) of the plasticizer.

The formed plastics, such as a film, comprising the poly(lactic acid)polymer composition of the first embodiment exhibits satisfactorydurability in use at ordinary temperatures or at relatively lowtemperatures.

Next, the poly(lactic acid) polymer composition of the second embodimentwill be illustrated below.

The poly(lactic acid) polymer composition of the second embodiment is apoly(lactic acid) polymer composition comprising a poly(lactic acid)polymer exhibiting crystallinity, a poly(lactic acid) polymer exhibitingno crystallinity, and a plasticizer, in which the plasticizer comprisesa polyether and/or polyester segment and has no poly(lactic acid)segment having a molecular weight of 1200 or more.

The poly(lactic acid) polymer composition of the second embodimentessentially comprises a poly(lactic acid) polymer exhibitingcrystallinity and a poly(lactic acid) polymer exhibiting nocrystallinity. When the poly(lactic acid) polymer composition comprisesnot a poly(lactic acid) polymer exhibiting no crystallinity but apoly(lactic acid) polymer exhibiting crystallinity alone, thecomposition exhibits high crystallinity and the resulting formedplastics shows excessively high crystallinity. Thus, the formed plasticsundergoes losing transparency in use under heating at a temperature of100° C. or below, such as in the case where the formed plastics comes incontact with boiling water or water vapor.

When a homopoly(lactic acid) is used as the poly(lactic acid)-polymerexhibiting crystallinity in the poly(lactic acid) polymer composition ofthe second embodiment, the homopoly(lactic acid) preferably has anoptical purity of about 75% or more.

When a homopoly(lactic acid) is used as the poly(lactic acid) polymerexhibiting no crystallinity in the poly(lactic acid) polymer compositionof the second embodiment, the homopoly(lactic acid) preferably has anoptical purity of less than about 70%.

The poly(lactic acid) polymer composition of the second embodimentfurther comprises a plasticizer. The plasticizer contained in thepoly(lactic acid) polymer composition of the second embodiment comprisesa polyether and/or polyester segment and does not have a poly(lacticacid) segment having a molecular weight of 1200 or more.

Next, the poly(lactic acid) polymer composition of the third embodimentwill be illustrated below.

The poly(lactic acid) polymer composition of the third embodiment is apoly(lactic acid) polymer composition comprising a poly(lactic acid)polymer exhibiting crystallinity and having a melting point lower than145° C., and a plasticizer, in which the plasticizer comprises apolyether and/or polyester segment and has no poly(lactic acid) segmenthaving a molecular weight of 1200 or more.

The poly(lactic acid) polymer composition of the third embodimentessentially comprises a poly(lactic acid) polymer exhibitingcrystallinity and having a melting point of lower than 145° C. Themelting point of the poly(lactic acid) polymer herein refers to a peaktemperature of crystal fusion as determined using a DSC at temperaturesranging from −30° C. to 220° C. at a temperature elevation rate of 20°C./min. If the poly(lactic acid) polymer composition of the thirdembodiment comprises a poly(lactic acid) polymer having a melting pointof 145° C. or higher alone, the poly(lactic acid) polymer compositionexhibits high crystallinity and the resulting formed plastics showsexcessively high crystallinity. Thus, the formed plastics undergoeslosing transparency in use under heating at a temperature of 100° C. orbelow, such as in the case where the formed plastics comes in contactwith boiling water or water vapor.

When a homopoly(lactic acid) is used as the poly(lactic acid) polymerhaving a melting point of lower than 145° C., the homopoly(lactic acid)preferably has an optical purity of less than about 88%.

The plasticizer contained in the poly(lactic acid) polymer compositionof the third embodiment comprises a polyether and/or polyester segmentand does not have a poly(lactic acid) segment having a molecular weightof 1200 or more.

In the poly(lactic acid) polymer compositions of the first, second andthird embodiments, the weight percentage of the poly(lactic acid)segment component in the plasticizer is preferably less than 50 percentby weight of the total plasticizer. By setting the weight percentage atless than 50 percent by weight based on the total weight of theplasticizer, the plasticizer shows relatively high plasticizingefficiency and can yield a poly(lactic acid) polymer composition havingdesired flexibility by the addition of the plasticizer in a smallamount. The-weight percentage of the poly(lactic acid) segment componentin the plasticizer is generally 5 percent by weight or more based on thetotal weight of the plasticizer, while depending on configurations suchas the proportion of the plasticizing component in the plasticizermolecule.

The weight percentage of the plasticizer in the poly(lactic acid)polymer compositions of the first, second and third embodiments ispreferably set according to required properties such as flexibility andstrength. In addition, the weight percentage of the plasticizingcomponent other than the poly(lactic acid) segment component in theplasticizer is preferably 5 percent by weight or more and 30 percent byweight or less based on the total weight of the composition. By settingthe weight percentage of the plasticizing component other than thepoly(lactic acid) segment component in the plasticizer at 5 percent byweight or more and 30 percent by weight or less of the totalcomposition, the resulting composition exhibits well-balanced mechanicalproperties such as flexibility and physical properties in strength.

Next, the poly(lactic acid) polymer composition of the fourth embodimentwill be illustrated.

The poly(lactic acid) polymer composition of the fourth embodiment is apoly(lactic acid) polymer composition which comprises a-poly(lacticacid) polymer exhibiting no crystallinity, and a plasticizer andcontains no poly(lactic acid) polymer exhibiting crystallinity, in whichthe plasticizer comprises a polyether and/or polyester segment.

The poly(lactic acid) polymer composition of the fourth embodimentessentially comprises a poly(lactic acid) polymer exhibiting nocrystallinity. When a homopoly(lactic acid) is used as the poly(lacticacid) polymer exhibiting no crystallinity, the homopoly(lactic acid)preferably has an optical purity of less than about 70%.

The poly(lactic acid) polymer composition of the fourth embodiment doesnot contain a poly(lactic acid) polymer exhibiting crystallinity.

Other components than the poly(lactic acid) segment of the plasticizerfor use in the poly(lactic acid) polymer composition of the fourthembodiment are preferably biodegradable components.

The poly(lactic acid) polymer composition of the fourth embodiment isespecially useful in use where the resulting formed plastics must beplastically deformed at relatively low temperatures, such as a heat sealcomponent of a multilayer film comprising a poly(lactic acid) polymer,although the composition does not have high heat resistance.

The poly(lactic acid) polymer compositions of the first, second, thirdand fourth embodiments may further comprise other components. Examplesof such components are, for example, known or conventional plasticizers,ultraviolet stabilizers, anticoloring agents, delustering agents,deodorants, flame retardants, weathering agents, antistatics, moldreleasing agents, antioxidants, ion exchanging agents, fine inorganicparticles and organic compounds serving as coloring pigments.

The other components are preferably biodegradable components when usedin the poly(lactic acid) polymer compositions of the first, second,third and fourth embodiments in addition to the poly(lactic acid)polymers and the plasticizer comprising a polyether and/or polyestersegment.

Examples of the known plasticizers to be contained in the poly(lacticacid) polymer compositions of the first, second, third and fourthembodiments are phthalic esters such as diethyl phthalate, dioctylphthalate and dicyclohexyl phthalate; aliphatic dibasic acid esters suchas di-1-butyl adipate, di-n-octyl adipate, di-n-butyl sebacate anddi-2-ethylhexyl azelate; phosphoric esters such as diphenyl-2-ethylhexylphosphate and diphenyloctyl phosphate; hydroxy-polycarboxylic acidesters such as tributyl acetylcitrate, tri-2-ethylhexyl acetylcitrateand tributyl citrate; fatty acid esters such as methyl acetylricinoleateand amyl stearate; polyhydric alcohol esters such as glycerol triacetateand triethylene glycol dicaprylate; epoxy plasticizers such-asepoxidized soybean oil, epoxidized linseed oil fatty acid butyl esterand octyl epoxystearate; polyester plasticizers such as poly(propyleneglycol) sebacic acid ester; poly(alkylene ether) plasticizers, etherester plasticizers and acrylate plasticizers. From the viewpoint ofsafety, plasticizers approved by Food and Drug Administration (FDA) arepreferably used.

The plasticizer is preferably added to the poly(lactic acid) polymer byadding the plasticizer to the poly(lactic acid) polymer after thecompletion of the polymerization reaction of the polymer, and meltingand kneading the resulting mixture. This increases the degree ofpolymerization of the poly(lactic acid) polymer and reduces residuallow-molecular-weight substances. Examples of the process for mixing,melting and kneading the plasticizer and the poly(lactic acid) polymerare a process in which the plasticizer is added to the poly(lactic acid)polymer in molten state immediately after the completion ofpolycondensation reaction, and the resulting mixture is agitated, meltedand kneaded; a process in which the plasticizer is mixed with chips ofthe poly(lactic acid) polymer, and the resulting mixture is melted andkneaded typically in a drum reactor or an extruder; a process in whichthe plasticizer which has been liquefied, where necessary, by heating iscontinuously added to the poly(lactic acid) polymer in an extruder, andthe resulting mixture is melted and kneaded; and a process in whichmaster chips of the poly(lactic acid) polymer containing a high contentof the plasticizer and homo-chips of the poly(lactic acid) polymer aremixed to yield blend chips, and the blend chips are melted and kneadedtypically in an extruder.

Examples of the antioxidants for use in the poly(lactic acid) polymercompositions of the first, second, third and fourth embodiments arehindered phenol antioxidants and hindered amine antioxidants.

Examples of the coloring pigments for use in the poly(lactic acid)polymer compositions of the first, second, third and fourth embodimentsare inorganic pigments such as carbon black, titanium oxide, zinc oxideand iron oxide; and organic pigments such as cyanine-, styrene-,phthalocyanine-, anthraquinone-, perinone-, isoindolinone-,quinophthalone-, quinacridone- and thioindigo-based pigments.

Fine inorganic particles may be added to the poly(lactic acid) polymercompositions of the first, second, third and fourth embodiments forimproving slidability (slipping property) and antiblocking property ofthe formed plastics. Examples of such fine inorganic particles aresilica, colloidal silica, alumina, alumina sol, kaolin, talc, mica andcalcium carbonate. The average particle size thereof is not specificallylimited and is preferably from 0.01 to 5 μm, more preferably from 0.05to 3 μm, and further preferably from 0.08 to 2 μm.

The poly(lactic acid) polymer compositions of the first, second, thirdand fourth embodiments may further comprise any of aliphatic polyestersother than the poly(lactic acid) polymers. Incorporation of aliphaticpolyesters other than the poly(lactic acid) polymers reduces the meltviscosity or improves the biodegradability.

Examples of the aliphatic polyesters other than the poly(lactic acid)polymers for use in the poly(lactic acid) polymer compositions of thefirst, second, third and fourth embodiments are poly(glycolic acid),poly(3-hydroxybutyrate), poly(3-hydroxybutyrate/3-hydroxyvalerate),polycaprolactone; and polyesters each comprising an aliphatic diol andan aliphatic dicarboxylic acid. Examples of the aliphatic diol areethylene glycol and 1,4-butanediol. Examples of the aliphaticdicarboxylic acid are succinic acid and adipic acid.

The poly(lactic acid) polymer compositions of the first, second andthird embodiments can be formed into formed plastics such as films andsheets from their molten or dissolved state.

The poly(lactic acid) polymer compositions of the first, second andthird embodiments exhibit satisfactory flexibility, transparency andphysical properties in strength and can be used in wider ranges ofapplications than conventional equivalents. They can be used, forexample, as packaging materials such as packaging wrap films and stretchfilms; industrial materials such as agricultural films, films forlabels, films for tapes, films for protecting base materials, sheets forprotecting automobile coatings, trash bags and compost bags; packagesand containers such as bottles for beverages or cosmetics, disposablecaps and trays; as well as nursery cabinets and flower pots.

The poly(lactic acid) polymer compositions of the first, second andthird embodiments can be formed into films according to a conventionalproduction process of a stretched film, such as blow-extrusion(inflation), sequential biaxial stretching or simultaneous biaxialstretching.

To prepare a film by sequential biaxial stretching or simultaneousbiaxial stretching, an unstretched film may be prepared by melting andextruding the poly(lactic acid) polymer composition from a slit die intoa sheet according to a conventional procedure, and allowing the sheet tocome in contact with a casting drum to thereby cool and solidify thecomposition.

For minimizing thermal degradation of the poly(lactic acid) polymercomposition, the plasticizer is preferably added to the poly(lacticacid) polymer by liquefying the plasticizer typically by heating,measuring and adding the liquefied plasticizer to the poly(lactic acid)polymer melted typically in a double-screw extruder, and melting andkneading the resulting mixture. It is also acceptable that master chipsof the poly(lactic acid) polymer containing a high content of theplasticizer and homo-chips of the poly(lactic acid) polymer are mixed toyield blend chips, and the blend chips are melted and kneaded typicallyin an extruding system of a film forming machine, such as an extruder.

To prepare a film, the above-prepared unstretched film is preferablycontinuously stretched in at least one direction and is subjected tothermal treatment according to necessity. A stretched film, for example,subjected to thermal treatment at a temperature of 100° C. or higher hassatisfactory dimensional stability, exhibits a low thermal shrinkage andis suitable typically as packaging wrap films and agricultural films. Astretched film without thermal treatment or one subjected to thermaltreatment at a temperature of lower than 100° C. has a high thermalshrinkage and is suitable as shrink packaging films.

The formed plastics, such as a film, comprising the poly(lactic acid)polymer composition of the first embodiment exhibits satisfactorydurability in use at ordinary temperatures or at relatively lowtemperatures.

The poly(lactic acid) polymer compositions of the second, third andfourth embodiments show markedly reduced losing transparency in useunder heating and exhibit satisfactory durability.

The poly(lactic acid) polymer compositions of the first, second andthird embodiments are typically effective in the fields of formedplastics such as films in which the evaporation, migration andextraction (bleedout) of the plasticizer may be avoided in many cases.

When the poly(lactic acid) polymer compositions of the first, second andthird embodiments, for example, are used as packaging wrap films, thepackaging wrap films exhibit practically satisfactory flexibility,transparency and physical properties in strength from immediately afterthe beginning of use, and show very small amount of the evaporation,migration and extraction (bleedout) of the plasticizer with elapse oftime in use and losing transparency in use under heating. The packagingwrap films can thereby maintain their initial flexibility andtransparency over a long period of time in use. The use of abiodegradable plasticizer yields packaging wrap films that can beconverted into compost without separation from the content such as foodafter use. The compositions exhibit satisfactory stability with time andcan yield formed plastics, such as films, that can exhibit initialperformance without deterioration even over a long time after thepreparation. The compositions also yield formed plastics, such as films,that stably exhibit flexibility and transparency even after dry thermalprocessing or treatment at high temperatures in after-processing stepsof the formed plastics. In addition, the resulting formed plastics donot undergo losing transparency even in use under heating.

The poly(lactic acid) polymer compositions of the first, second andthird embodiments can be stretched 1.1 times or more in at least oneaxial direction to yield formed plastics such as films.

The films comprising the poly(lactic acid) polymer compositions of thefirst, second and third embodiments are often prepared by stretching thecompositions 1.1 times or more in at least one axial direction. To avoidununiform stretching under some stretching conditions such as stretchingtemperature and stretching (deformation) speed, the compositions arepreferably stretched 2 times or more, and more preferably 2.5 times ormore to yield films.

By stretching the poly(lactic acid) polymer composition of the firstembodiment 1.1 times or more in at least one axial direction to yield afilm, the matrix poly(lactic acid) polymer is further highly orientedand crystallized, and the poly(lactic acid) segment of the plasticizeris further incorporated into the crystal. Thus, the resulting film isfurther prevented from the evaporation, migration and extraction(bleedout) of the plasticizer. The orientation and crystallization alsoimproves the physical properties in strength of the film, and the filmexhibits both satisfactory flexibility and strength.

To prepare biaxially stretched films from the poly(lactic acid) polymercompositions of the first, second and third embodiments, thecompositions are stretched preferably 4 times or more, and morepreferably 7 times or more in terms of areal magnification ratio as anareal ratio of the film between before and after stretching.

The films derived from the poly(lactic acid) polymer compositions of thefirst, second and third embodiments preferably each have a tensilemodulus of elasticity of 100 to 1500 MPa. The tensile modulus ofelasticity of such a film can be set at a desired level by controllingthe amount and type of the plasticizer in the composition, andfilm-forming conditions. The tensile modulus of elasticity is preferablyset at 1500 MPa or less. This gives good usability to the films in theapplications such as trash bags, agricultural mulch films, stretchfilms, films for labels, films for tapes, films for protecting basematerials, films for bags, and packaging films. In addition, the aboveconfiguration easily gives sufficient adhesion to the films when theyare used as wrap films for food packaging, since the films sufficientlydeform in accordance with the shape of a material to be packaged. Bysetting the tensile modulus of elasticity at 100 MPa or more, theresulting films can be satisfactorily unwound when they are wound as aroll, and can pass through the film-forming and processing processes.

The films derived from the poly(lactic acid) polymer compositions of thefirst, second and third embodiments preferably each have a heatresistance of 120° C. to 230° C. The heat resistance of the films isdetermined according to a method described in the examples. The filmshaving a heat resistance of 120° C. or higher are substantially freefrom adhesion to a heating roller during film-formation and stretching,adhesion to members during heat setting, and blocking afterfilm-formation and are excellent in process stability. In addition, theresulting films when used as wrap films for food packaging aresubstantially free from breaking, or melting and deposition onto anarticle to be packaged, even when they are brought into contact with hotwater or heated in a microwave oven.

The films derived from the poly(lactic acid) polymer compositions of thefirst, second and third embodiments each mainly comprise the poly(lacticacid) polymer. The melting point of the poly(lactic acid) is generallyat highest 230° C., and the upper limit of the heat resistance of thefilms is pursuant to this.

A poly(L-lactic acid) has a melting point of about 170° C. even at anoptical purity of 98% or more. In contrast, a “stereo complex crystal”has a melting point of about 220° C. to about 230° C. In the stereocomplex crystal, poly(lactic acid) molecules of optical isomers (forexample, a poly(L-lactic acid) and a poly(D-lactic acid)) constitute thecrystal in a pair. A combination use of, for example, a poly(L-lacticacid) and a poly(D-lactic acid) each having an optical purity of 95% ormore as the poly(lactic acid) polymer is preferred to impart heatresistance of higher than 170° C. to formed plastics, typically films,derived from the poly(lactic acid) polymer compositions of the first,second and third embodiments.

The formed plastics, especially a film, derived from the poly(lacticacid) polymer composition of the first embodiment may have aconfiguration in which the poly(lactic acid) polymer is, for example, apoly(L-lactic acid) having an optical purity of 95% or more, and thepoly(lactic acid) segment of the plasticizer is one comprising 98percent by weight or more of a component derived from D-lactic acid.

The poly(lactic acid) polymer compositions of the first, second andthird embodiments each preferably contain equivalent amounts orsubstantially equivalent amounts of a component derived from L-lacticacid and a component derived from D-lactic acid, in order to furtheraccelerate the formation of the stereo complex crystal in the formedplastics, especially films, derived from the compositions.

The films derived from the poly(lactic acid) polymer compositions of thefirst, second and third embodiments inherently have satisfactorytransparency and preferably each have a film haze of 0.2% to 5%. Thefilm haze herein refers to a film haze which is measured by a methoddescribed in the examples and is converted in terms of a film thicknessof 10 μm according to a proportional calculation. A film having a filmhaze of 0.2% to 5% is suitable as a packaging wrap film, typically as awrap film for food packaging, since the content can be easily seen. Foruse in applications which require certain masking property or require alow optical transmittance or a high absorptivity with respect to solarlight, as in trash bags and agricultural mulch films, coloring pigments,for example, may be added according to necessity.

The films derived from the poly(lactic acid) polymer compositions of thefirst, second and third embodiments preferably each have an adhesion of5 to 30 N/cm². The adhesion herein is determined by a method describedin the examples. A film having an adhesion of 5 to 30 N/cm² is suitablyused as a wrap film for food packaging. The resulting packaging wrapfilm is free from spontaneous peeling off during use due to insufficientadhesion and is free from deteriorated releasability from a roll due toblocking. It can be smoothly taken out from a roll, exhibits appropriateadhesiveness in use and has satisfactory usability.

The thickness of the films derived from the poly(lactic acid) polymercompositions of the first, second and third embodiments is notspecifically limited and can be set at an appropriate thicknessaccording to the application. The thickness of the films is generally 5μm or more and 1 mm or less, and is preferably 5 μm or more and 200 μmor less. As packaging wrap films, typically as wrap films for foodpackaging, the thickness is preferably set within a range of 5 μm ormore and 25 μm or less.

The films derived from the poly(lactic acid) polymer compositions of thefirst, second and third embodiments may be subjected to surfacetreatment after film-formation for the purpose of improving, forexample, printability, lamination suitability or coating suitability.Examples of the surface treatment are corona discharge treatment, plasmatreatment, flame treatment and acid treatment, and any of them can beused. Among them, corona discharge treatment is most preferable as thesurface treatment, since corona discharge treatment can be carried outcontinuously and easily, and facilities for the treatment can be easilyarranged in already existed film-forming facilities.

EXAMPLES

This disclosure will be illustrated in further detail with reference toseveral examples below, which are not intended to limit the scope of theappended claims.

In the following examples, the weight loss rate after dry heat treatmentand the weight loss rate after treatment with hot water were determinedas accelerating tests on the evaporation, migration and extraction(bleedout) of a plasticizer. The physical properties in the exampleswere determined by the following methods.

(1) Bending Modulus of Elasticity [MPa]

A bending test (Japanese Industrial Standards (JIS) K 6911) was carriedout using a Tensilon universal tester Model RTC-1310 (ORIENTEC CO.). Atest piece 12 mm wide and 6 mm thick was subjected to the-test in anatmosphere at 30° C. at a distance between clamps of 120 mm and a testspeed of 3 mm/min.

(2) Weight Loss Rate After Dry Heat Treatment [%]

After subjecting to moisture conditioning at a temperature of 23° C. andrelative humidity of 65% for one day or longer, a sample pressed sheetor biaxially stretched film was weighed to determine a weight beforeheat treatment. Next, the sample was treated in a hot-air oven at 90° C.for 30 minutes, was then subjected to moisture conditioning under thesame conditions as before the treatment and was weighed. The weight lossrate was determined as a percentage of change in weight (weight loss)between before and after the treatment based on the weight before thetreatment.

(3) Weight Loss Rate After Hot-Water Treatment [%]

After subjecting to moisture conditioning at a temperature of 23° C. andrelative humidity of 65% for one day or longer, a sample pressed sheetor biaxially stretched film was weighed to determine a weight beforeheat treatment. Next, the sample was treated in distilled water at 90°C. for 30 minutes, was then subjected to moisture conditioning under thesame conditions as before the treatment and was weighed. The weight lossrate was determined as a percentage of change in weight (weight loss)between before and after the treatment based the weight before thetreatment.

(4) Transparency Retention Temperature [° C.]

A test sample pressed sheet or film was attached under a tension withoutwrinkle to an aluminum frame having an inside size of 150 mm square, wasfixed to the frame using a plurality of alligator clips for stationaryand was left in a hot-air oven held at a set temperature for 30 minutes.The sample was then taken out from the oven and was visually observed.The test procedure was repeated while changing the set temperature ofthe hot-air oven in steps of 5° C. In this procedure, the transparencyretention temperature was defined as a highest temperature at which thesample did not undergo losing transparency and showed no change intransparency.

(5) Heat of Crystal Fusion (ΔH_(po)) [J/g]

A sample plasticizer was subjected in advance to treatment at 90° C.under a reduced pressure of 1 torr or less for 3 hours for sufficientdrying and crystallization. If the plasticizer has a melting point of90° C. or lower, the sample plasticizer was subjected to measurementwithout the drying and crystallization treatment. About 5 mg of thesample was precisely weighed, was charged into a predetermined samplepan and was subjected to temperature elevation from −30° C. to 220° C.at a rate of 20° C./min in an atmosphere of nitrogen using adifferential scanning calorimeter (DSC) RDC 220 available from SeikoInstruments Inc. The heat of crystal fusion derived from a poly(lacticacid) segment of the plasticizer was read out from the resultingthermograph.

(6) Tensile Modulus of Elasticity [MPa]

A sample film piece 10 mm wide and 150 mm long was subjected to moistureconditioning at a temperature of 23° C. and relative humidity of 65% forone day or longer in advance. The resulting film piece was subjected toa tensile test at 23° C. and at a distance between clamps of 50 mm and atensile speed of 300 mm/min., using a Tensilon universal tester ModelUTC-100 (ORIENTEC CO.) to determine a tensile modulus of elasticity. Themeasuring procedure was repeated a total of ten times, namely, fivetimes in a longitudinal direction and five times in a widthwisedirection per one level. In this procedure, the tensile modulus ofelasticity was defined as the average of ten measurements.

(7) Heat Resistance [° C.]

A test sample pressed sheet or film was attached under a tension withoutwrinkle to an aluminum frame having an inside size of 150 mm square, wasfixed to the frame using a plurality of alligator clips for stationary,and was left in a hot-air oven held at a set temperature for 5 minutes.The sample was then taken out from the oven and was visually observed.The test procedure was repeated while changing the set temperature ofthe hot-air oven in steps of 5° C. In this procedure, the temperatureindicating the heat resistance was defined as a highest temperature atwhich the sample did not show a change such as breakage or fusion to theframe.

(8) Film Haze [%]

The thickness of a sample film was determined in advance, and the hazeof the sample film as an index of transparency thereof was determinedusing a Haze meter Model HGM-2DP (a product of Suga Test Instruments).The measurement procedure was repeated a total of five times per onelevel, and the film haze (%) was determined in terms of a film 10 μmthick based on the average of the five measurements.

(9) Adhesion [N/cm²]

A pair of two film pieces 10 mm wide and 100 mm long was prepared andwas subjected to humidity conditioning at a temperature of 23° C. andrelative humidity of 65% for one day or longer. Subsequently, a portion10 mm in a longitudinal direction from the edge of one film piece waslaid over a portion 10 mm in a longitudinal direction from the edge ofthe other film piece under the same atmosphere so that the longitudinaldirection of one film piece met with that of the other. A load of 50g/cm² was applied to the overlaid portion for one minute to therebyyield a test sample for measurement of adhesion. The adhesion wasdetermined using a Tensilon universal tester Model UTC-100 (ORIENTECCO.). The above-mentioned test sample was set into the tester so thatthe overlaid portion stood substantially at the center between clamps. Atensile test was carried out at a distance between the clamps of 50 mmand a tensile speed of 300 mm/min. in an atmosphere of 23° C., and astress immediately before the overlaid portion peeled off was measured.When the film pieces had a relatively low tensile strength and anotherportion than the overlaid portion was broken before the overlaid portionpeeled off, each two thicknesses were fully overlaid to give testpieces, and a pair of two overlaid test pieces were subjected to theabove mentioned test procedure. The measurement procedure was repeated atotal of five times per one level, and the adhesion was defined as anaverage of the five measurements.

Poly(lactic acid) polymers and plasticizers used in the examples wereprepared in the following manner.

<Poly(lactic acid) polymer (P1)>

A total of 0.02 part by weight of tin octylate was added to 100 parts byweight of L-lactide, followed by polymerization at 190° C. in anatmosphere of nitrogen for 15 minutes in a reactor equipped with astirrer. The reaction mixture was formed into chips using a double-screwkneader-extruder, followed by solid-phase polymerization at 140° C. inan atmosphere of nitrogen for 3 hours to thereby yield a poly(lacticacid) polymer P1. P1 was subjected to DSC measurement and was found toexhibit crystallinity and to have a crystallization temperature of 128°C. and a melting point of 172° C.

<Poly(lactic acid) polymer (P2)>

A total of 0.02 part by weight of tin octylate was added to 65 parts byweight of L-lactide and 35 parts by weight of DL-lactide, followed bypolymerization at 190° C. in an atmosphere of nitrogen for 40 minutes ina reactor equipped with a stirrer. The reaction mixture was formed intochips using a double-screw kneader-extruder to yield a poly(lactic acid)polymer P2. P2 was subjected to DSC measurement and was found that P2did not exhibit crystallinity and that no crystallization temperatureand melting point were observed.

<Poly(Lactic Acid) Polymer (P3)>

A total of 0.02 part by weight of tin octylate was added to 86 parts byweight of L-lactide and 14 parts by weight of DL-lactide, followed bypolymerization at 190° C. in an atmosphere of nitrogen for 40 minutes ina reactor equipped with a stirrer. The reaction mixture was formed intochips using a double-screw kneader-extruder to yield a poly(lactic acid)polymer P3. P3 was subjected to DSC measurement and was found to exhibitcrystallinity and to have a melting point of 141° C.

<Plasticizer (S1)>

A total of 0.025 part by weight of tin octylate was added to 40 parts byweight of a poly(1,3-butanediol adipate) having an average molecularweight of 8,000 and 60 parts by weight of L-lactide, followed bypolymerization at 190° C. in an atmosphere of nitrogen for 60 minutes ina reactor equipped with a stirrer, to yield a block copolymer Si betweenpoly(1,3-butanediol-adipate) and poly(lactic acid). The block copolymerhad poly(lactic acid) segments each having an average molecular weightof 6000 at both ends. S1 was found to have a ΔH_(po) of 23.3 J/g and apeak temperature in ΔH_(po) of 145.0° C.

<Plasticizer (S2)>

A total of 0.025 part by weight of tin octylate was added to 71 parts byweight of a poly(1,3-butanediol adipate) having an average molecularweight of 10000 and 29 parts by weight of L-lactide, followed bypolymerization at 190° C. in an atmosphere of nitrogen for 60 minutes ina reactor equipped with a stirrer, to yield a block copolymer S2 betweenpoly(1,3-butanediol adipate) and poly(lactic acid). The block copolymerhad poly(lactic acid) segments each having an average molecular weightof 2,000 at both ends. S2 was found to have a ΔH_(po) of 11.4 J/g and apeak temperature in ΔH_(po) of 124.1° C.

<Plasticizer (S3)>

A poly(propylene glycol)/(ethylene glycol) block copolymer having amolecular weight of 10000 was prepared by adding ethylene oxide to bothends of a poly(propylene glycol) having an average molecular weight of2000. A total of 0.025 part by weight of tin octylate was added to 71parts by weight of the block copolymer and 29 parts by weight ofL-lactide, followed by polymerization at 190° C. in an atmosphere ofnitrogen for 60 minutes in a reactor equipped with a stirrer, to yield ablock copolymer S3 between poly(propylene glycol)/(ethylene glycol) andpoly(lactic acid). The resulting block copolymer had poly(lactic acid)segments each having an average molecular weight of 2000 at both ends.S3 was found to have a ΔH_(po) of 15.8 J/g and a peak temperature inΔH_(po) of 131.8° C.

<Plasticizer (S4)>

A total of 0.025 part by weight of tin octylate was added to 71 parts byweight of a poly(ethylene glycol) having an average molecular weight of10000 and 29 parts by weight of L-lactide, followed by polymerization at190° C. in an atmosphere of nitrogen for 60 minutes in a reactorequipped with a stirrer, to yield a block copolymer S4 betweenpoly(ethylene glycol) and poly(lactic acid). The block copolymer hadpoly(lactic acid) segments each having an average molecular weight of2000 at both ends. S4 was found to have a ΔH_(po) of 17.0 J/g and a peaktemperature in ΔH_(po) of 135.0° C.

<Plasticizer (S5)>

An ether ester plasticizer “RS-1000” (liquid at room temperature), aproduct of Asahi Denka Kogyo K.K., was used as a plasticizer S5.

<Plasticizer (S6)>

A poly(ethylene glycol) having an average molecular weight of 8000 wasused as a plasticizer S6.

<Plasticizer (S7)>

A total of 0.025 part by weight of tin octylate was added to 80 parts byweight of a poly(ethylene glycol) having an average molecular weight of8000 and 20 parts by weight of L-lactide, followed by polymerization at190° C. in an atmosphere of nitrogen for 60 minutes in a reactorequipped with a stirrer, to yield a block copolymer S7 betweenpoly(ethylene glycol) and poly(lactic acid). The block copolymer hadpoly(lactic acid) segments each having an average molecular weight of1000 at both ends. The ΔH_(po) of S7 was not observed.

<Plasticizer (S8)>

A total of 0.025 part by weight of tin octylate was added to 79 parts byweight of a poly(ethylene glycol) having an average molecular weight of10000 and 21 parts by weight of L-lactide, followed by polymerization at190° C. in an atmosphere of nitrogen for 60 minutes in a reactorequipped with a stirrer, to yield a block copolymer S8 betweenpoly(ethylene glycol) and poly(lactic acid). The block copolymer hadpoly(lactic acid) segments each having an average molecular weight of1300 at both ends. S8 was found to have a ΔH_(po) of 9.2 J/g and a peaktemperature in ΔH_(po) of 122.0° C.

The number-average molecular weight of the poly(lactic acid) segment wasfound to be 1260 as determined by calculation according to the followingequation:Number−average molecular weight=(½)×(I _(PLA)×72)/(I _(PEG)×44/4)×M_(PEG)wherein I_(PEG) is the integrated intensity of signals derived fromhydrogen of the methylene group of the principal chain of PEG; I_(PLA)is the integrated intensity of signals derived from hydrogen of themethine group of the principal chain of PLA; and M_(PEG) is the averagemolecular weight of the poly (ethylene glycol), based on a chartobtained by subjecting a solution of the plasticizer (S8) in deuteriumchloroform to 1H-NMR measurement. This value very satisfactorilycorresponded to a value calculated according to the formula:(½)×(w_(A)/w_(B))×M_(PEG)wherein w_(A) is the parts by weight of L-lactide; w_(B) is the parts byweight of the poly (ethylene glycol); and M_(PEG) is the averagemolecular weight of the poly (ethylene glycol), based on the chargedproportions of the raw materials.<Plasticizer (S9)>

A total of 0.025 part by weight of tin octylate was added to 71 parts byweight of a poly(ethylene glycol) monomethyl ether having an averagemolecular weight of 10000 and 29 parts by weight of L-lactide, followedby polymerization at 190° C. in an atmosphere of nitrogen for 60 minutesin a reactor equipped with a stirrer, to yield a block copolymer S9between poly(ethylene glycol) and poly(lactic acid). The block copolymerhad a poly(lactic acid) segment having an average molecular weight of4000 at one end. S9 was found to have a ΔH_(po) of 21.8 J/g and a peaktemperature in ΔH_(po) of 134.8° C.

<Inorganic Particle (F1)>

A commercially available calcium carbonate powder was used as aninorganic particle F1.

Example 1

A mixture of 50 parts by weight of the poly(lactic acid) polymer (P1)and 50 parts by weight of the plasticizer (S1) was dried at 100° C.under reduced pressure for 6 hours, was melted, kneaded and homogenizedin a double-screw kneader-extruder at a cylinder temperature of 200° C.,and the kneaded product was extruded into chips to yield a chip-formcomposition. The resulting composition was optically transparent.

This composition was molded into a test piece for bending modulus ofelasticity 12 mm wide and 6 mm thick using an injection molding machineat a barrel temperature of 200° C. and a die temperature of 20° C. Thecomposition was also molded into a pressed sheet 200 μm thick by hotpressing at 190° C. The properties of the test piece and the pressedsheet were determined, and the results are shown in Table 1.

Example 2

A chip-form composition was prepared by the procedure of Example 1,except for using a mixture of 72 parts by weight of the poly(lacticacid) polymer (P1) and 28 parts by weight of the plasticizer. (S2). Theresulting composition was optically transparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 1.

Example 3

A chip-form composition was prepared by the procedure of Example 1,except for using a mixture of 51 parts by weight of the poly(lacticacid) polymer (P1) and 49 parts by weight of the plasticizer (S2). Theresulting composition was slightly opaque but substantially opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 1.

Example 4

A chip-form composition was prepared by the procedure of Example 1,except for using a mixture of 72 parts by weight of the poly(lacticacid) polymer (P1), 28 parts by weight of the plasticizer (S3) and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting composition was opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 1.

Example 5

A chip-form composition was prepared by the procedure of Example 1,except for using a mixture of 94 parts by weight of the poly(lacticacid) polymer (P1), 6 parts by weight of the plasticizer (S3) and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting composition was opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 1.

Example 6

A chip-form composition was prepared by the procedure of Example 1,except for using a mixture of 72 parts by weight-of the poly(lacticacid) polymer (P1), 28 parts by weight of the plasticizer (S4) and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting composition was opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 1.

Example 7

A pressed sheet was prepared by the procedure of Example 6 and wassubjected to simultaneous biaxial stretching at a stretching temperatureof 70° C., draw ratios in longitudinal and transverse directions of each3.2 times and an areal ratio of 10 times, followed by heat treatment inan atmosphere at 140° C. for 20 seconds to yield a biaxially stretchedfilm. The resulting biaxially stretched film was optically transparent.The properties of the biaxially stretched film were determined, and theresults are shown in Table 1.

Example 8

A chip-form composition was prepared by the procedure of Example 1,except for using a mixture of 75 parts by weight of the poly(lacticacid) polymer (P1), 25 parts by weight of the plasticizer (S8) and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting composition was opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 1.

Example 9

A mixture of 37 parts by weight of the poly(lactic acid) polymer (P1)and 28 parts-by weight of the plasticizer (S4) both of which had beendried at 100° C. under reduced pressure for 6 hours, 35 parts by weightof the poly(lactic acid) polymer (P2) which had been dried at 50° C.under reduced pressure for 48 hours or longer, and 0.3 part by weight ofa hindered phenol antioxidant “Irganox 1010,” a product of Ciba-GeigyLtd., was melted, kneaded and homogenized in a double-screwkneader-extruder at a cylinder temperature of 200° C., and the kneadedproduct was extruded into chips to yield a chip-form composition. Theresulting composition was optically transparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 1.

Example 10

A chip-form composition was prepared by the procedure of Example 9,except for using a mixture of 45 parts by weight of the poly(lacticacid) polymer (P1) which had been dried at 100° C. under reducedpressure for 6 hours, 20 parts by weight of the plasticizer (S6), 35parts by weight of the poly(lactic acid) polymer (P2) which had beendried at 50° C. under reduced pressure for 48 hours or longer, and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting composition was opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 2.

Example 11

A chip-form composition was prepared by the procedure of Example 9,except for using a mixture of 80 parts by weight of the poly(lacticacid) polymer (P3)—which had been dried at 80° C. under reduced pressurefor 12 hours, 20 parts by weight of the plasticizer (S6) and 0.3 part byweight of a hindered phenol antioxidant “Irganox 1010,” a product ofCiba-Geigy Ltd. The resulting composition was optically transparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 3.

Example 12

A composition was prepared by the procedure of Example 6, except forusing the plasticizer (S9) instead of the plasticizer (S4). Theresulting composition was optically transparent. This composition wasmolded into a test piece for bending modulus of elasticity by theprocedure of Example 1. The composition was also molded into a pressedsheet 200 μm thick by hot pressing at 190° C. The properties of the testpiece and the pressed sheet were determined, and the results are shownin Table 1.

Example 13

A chip-form composition was prepared by the procedure of Example 9,except for using a mixture of 72 parts by weight of the poly(lacticacid) polymer (P2) which had been dried at 50° C. under reduced pressurefor 48 hours or longer, 28 parts by weight of the plasticizer (S4) whichhad been dried at 100° C. under reduced pressure for 6 hours, and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting composition was opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Table 4.

Comparative Example 1

A test piece for bending modulus of elasticity was prepared by theprocedure of Example 1, except for using the poly(lactic acid) polymer(P1) alone without the use of the plasticizer. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Tables 1, 2, 3 and 4.

Comparative Example 2

A mixture of 80 parts by weight of the poly(lactic acid) polymer (P1)which had been dried at 100° C. under reduced pressure for 6 hours and20 parts by weight of the commercially available ether ester plasticizer(S5) was melted, kneaded and homogenized in a double-screwkneader-extruder at a cylinder temperature of 200° C., and the kneadedproduct was extruded into chips to yield a chip-form composition. Theresulting composition was optically transparent.

This composition was molded into a test piece for bending modulus ofelasticity 12 mm wide and 6 mm thick using an injection molding machineat a barrel temperature of 200° C. and a die temperature of 20° C. Thecomposition was also molded into a pressed sheet 200 μm thick by hotpressing at 190° C. The properties of the test piece and the pressedsheet were determined, and the results are shown in Tables 1, 2, 3 and4.

Comparative Example 3

A chip-form composition was prepared by the procedure of ComparativeExample 2, except for using a mixture of 80 parts by weight of thepoly(lactic acid) polymer (P1) which had been dried at 100° C. underreduced pressure for 6 hours, 20 parts by weight of the plasticizer (S6)having no poly(lactic acid) segment having a molecular weight of 1200 ormore, and 0.3 part by weight of a hindered phenol antioxidant “Irganox1010,” a product of Ciba-Geigy Ltd. Neither the poly(lactic acid)polymer (P2) exhibiting no crystallinity nor the poly(lactic acid)polymer (P3) exhibiting crystallinity and having a melting point lowerthan 145° C. was added. The resulting composition was opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Tables 1, 2, 3 and 4.

Comparative Example 4

A chip-form composition was prepared by the procedure of ComparativeExample 2, except for using a mixture of 75 parts by weight of thepoly(lactic acid) polymer (P1) which had been dried at 100° C. underreduced pressure for 6 hours, 25 parts by weight of the plasticizer (S7)having no poly(lactic acid) segment having a molecular weight of 1200 ormore, and 0.3 part by weight of a hindered phenol antioxidant “Irganox1010,” a product of Ciba-Geigy Ltd. Neither the poly(lactic acid)polymer (P2) exhibiting no crystallinity nor the poly(lactic acid)polymer (P3) exhibiting crystallinity and having a melting point lowerthan 145° C. was added. The resulting composition was opticallytransparent.

This composition was molded into a test piece for bending modulus ofelasticity by the procedure of Example 1. The composition was alsomolded into a pressed sheet 200 μm thick by hot pressing at 190° C. Theproperties of the test piece and the pressed sheet were determined, andthe results are shown in Tables 1, 2, 3 and 4.

Comparative Example 5

A pressed sheet was prepared by the procedure of Comparative Example 4and was subjected to simultaneous biaxial stretching at a stretchingtemperature of 70° C., draw ratios in longitudinal and transversedirections of each 3.2 times and an areal ratio of 10 times, followed byheat treatment in an atmosphere at 140° C. for 20 seconds to yield abiaxially stretched film. The resulting biaxially stretched film wasoptically transparent. The properties of the biaxially stretched filmwere determined, and the results are shown in Tables 1, 2, 3 and 4.

TABLE 1 Weight percentage of Weight Poly (lactic acid) Molecular poly(lactic percentage of Weight Weight polymer// weight of poly acid)plasticizing Bending loss after loss after Transparency plasticizer(lactic acid) segment in component in modulus of dry heat hot-waterretention (weight segment in plasticizer composition elasticitytreatment treatment temperature percentage) plasticizer [weight %][weight %] [MPa] [%] [%] [° C.] Ex. 1 P1//S1 (50//50) 6000 60 20 911 0.81.3 110 Ex. 2 P1//S2 (72//28) 2000 29 20 957 0.9 1.4 115 Ex. 3 P1//S2(51//49) 2000 29 35 636 1.2 1.7 105 Ex. 4 P1//S3 (72//28) 2000 29 20 1920.6 0.9 120 Ex. 5 P1//S3 (94//6) 2000 29 4 694 0.2 0.2 130 Ex. 6 P1//S4(72//28) 2000 29 20 44 0.4 0.7 120 Ex. 7 P1//S4 (72//28) 2000 29 20 —0.2 0.2 110 Ex. 8 P1//S8 (75//25) 1300 21 20 60 0.7 1.1 120 Ex. 9P1/P2//S4 2000 29 20 40 0.5 0.8 125 (37/35/28) Ex. 12 P1//S9 (72//28)4000 29 20 71 0.3 0.8 120 Com. Ex. 1 P1 (100) — — 0 2550 0.1 0.1 ≧140Com. Ex. 2 P1/S5 (80//20) 0 0 20 111 0.4 19.2 90 Com. Ex. 3 P1//S6(80//20) 0 0 20 52 2.5 3.8 90 Com. Ex. 4 P1//S7 (75//25) 1000 20 20 462.3 3.4 90 Com. Ex. 5 P1//S7 (75//25) 1000 20 20 — 2.2 3.1 85

TABLE 2 Weight Molecular percentage of Weight Poly (lactic acid) weightof poly (lactic percentage of Weight Weight polymer// poly acid)plasticizing Bending loss after loss after Transparency plasticizer(lactic acid) segment in component in modulus of dry heat hot-waterretention (weight segment in plasticizer composition elasticitytreatment treatment temperature percentage) plasticizer [weight %][weight %] [MPa] [%] [%] [° C.] Ex. 10 P1/P2//S6 0 0 20 49 1.7 2.0 125(45/35//20) Com. Ex. 1 P1 (100) — — 0 2550 0.1 0.1 ≧140 Com. Ex. 2P1//S5 (80//20) 0 0 20 111 0.4 19.2 90 Com. Ex. 3 P1//S6 (80//20) 0 0 2052 2.5 3.8 90 Com. Ex. 4 P1//S7 (75//25) 1000 20 20 46 2.3 3.4 90 Com.Ex. 5 P1//S7 (75//25) 1000 20 20 — 2.2 3.1 85

TABLE 3 Weight Molecular percentage of Weight Poly (lactic acid) weightof poly (lactic percentage of Weight Weight polymer// poly acid)plasticizing Bending loss after loss after Transparency plasticizer(lactic acid) segment in component in modulus of dry heat hot-waterretention (weight segment in plasticizer composition elasticitytreatment treatment temperature percentage) plasticizer [weight %][weight %] [MPa] [%] [%] [° C.] Ex. 11 P3//S6(80//20) 0 0 20 55 1.6 1.9105 Com. Ex. 1 P1 (100) — — 0 2550 0.1 0.1 ≧140 Com. Ex. 2 P1//S5(80//20) 0 0 20 111 0.4 19.2 90 Com. Ex. 3 P1//S6 (80//20) 0 0 20 52 2.53.8 90 Com. Ex. 4 P1//S7 (75//25) 1000 20 20 46 2.3 3.4 90 Com. Ex. 5P1//S7 (75//25) 1000 20 20 — 2.2 3.1 85

TABLE 4 Weight Molecular percentage of Weight Poly (lactic acid) weightof poly (lactic percentage of Weight Weight polymer// poly acid)plasticizing Bending loss after loss after Transparency plasticizer(lactic acid) segment in component in modulus of dry heat hot-waterretention (weight segment in plasticizer composition elasticitytreatment treatment temperature percentage) plasticizer [weight %][weight %] [MPa] [%] [%] [° C.] Ex. 13 P2//S4 (72//28) 2000 29 20 46 2.13.0 ≧140 Com. Ex. 1 P1 (100) — — 0 2550 0.1 0.1 ≧140 Com. Ex. 2 P1//S5(80//20) 0 0 20 111 0.4 19.2 90 Com. Ex. 3 P1//S6 (80//20) 0 0 20 52 2.53.8 90 Com. Ex. 4 P1//S7 (75//25) 1000 20 20 46 2.3 3.4 90 Com. Ex. 5P1//S7 (75//25) 1000 20 20 — 2.2 3.1 85

Example 14

A mixture of 57 parts by weight of the poly(lactic acid) polymer (P1)and 43 parts by weight of the plasticizer (S2), both of which had beendried at 100° C. under reduced pressure for 6 hours, was melted, kneadedand homogenized in a double-screw kneader-extruder at a cylindertemperature of 200° C., and the kneaded product was extruded into chipsto yield a chip-form composition. The resulting composition wasoptically transparent. The composition (chips) was dried at 80° C. underreduced pressure for 24 hours or longer before subjecting to thefollowing film-formation.

The chips were melted in a single-screw extruder at a set meltingtemperature of 210° C., the melted polymer was introduced to a T-diehead to extrude into a sheet, the sheet was cast on a drum cooled atabout 5° C. and thereby yielded an unstretched film. The unstretchedfilm was continuously stretched 3.5 times in a longitudinal directionbetween heating rolls at 60° C. and was then stretched in a widthwisedirection at 65° C. at a set draw ratio of 3.0 times using a tenterstretching apparatus, followed by heat treatment at 130° C. under atension. The resulting film was wound up. The resulting film had athickness of 12 micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 5.

Example 15

A biaxially stretched film was prepared by the procedure of Example 14,except for using a mixture of 72 parts by weight of the poly(lacticacid) polymer (P1) and 28 parts by weight of the plasticizer (S3). Theresulting film had a thickness of 15 micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 5.

Example 16

A biaxially stretched film was prepared by the procedure of Example 14,except for using a mixture of 86 parts by weight of the poly(lacticacid) polymer (P1), 14 parts by weight of the plasticizer (S4) and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting film had a thickness of 40micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 5.

Example 17

A biaxially stretched film was prepared by the procedure of Example 14,except for using a mixture of 72 parts by weight of the poly(lacticacid) polymer (P1), 28 parts by weight of the plasticizer (S4) and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting film had a thickness of 18micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 5.

Example 18

A biaxially stretched film was prepared by the procedure of Example 14,except for using a mixture of 70 parts by weight of the poly(lacticacid) polymer (P1), 28 parts by weight of the plasticizer (S4), 2 partsby weight of the inorganic particle (F1) and 0.3 part by weight of ahindered phenol antioxidant “Irganox 1010,” a product of Ciba-Geigy Ltd.The resulting film had-a thickness of 38 micron.

The properties-of the biaxially stretched film were determined, and theresults are-shown in Table 5.

Example 19

A mixture of 17 parts by weight of the poly(lactic acid) polymer (P1)and 28 parts by weight of the plasticizer (S4) both of which had beendried at 100° C. under reduced pressure for 6 hours, 55 parts by weightof the poly(lactic acid) polymer (P2) which had been dried at 50° C.under reduced pressure for 48 hours or longer, and 0.3 part by weight ofa hindered phenol antioxidant “Irganox 1010,” a product of Ciba-GeigyLtd., was melted, kneaded and homogenized in a double-screwkneader-extruder at a cylinder temperature of 200° C., and the kneadedproduct was extruded into chips to yield a chip-form composition. Thecomposition (chips) was dried at 70° C. under reduced pressure for 24hours or longer and was subjected to the following film-formation.

The chips were melted in a single-screw extruder at a set meltingtemperature of 210° C., the melted polymer was introduced to a circulardie, was extruded into a tube and was rapidly cooled using cold water atabout 5° C. The cooled tube was subjected to simultaneous biaxialstretching at draw ratios of 4 times in a longitudinal direction and 4times in a widthwise direction under heating at 55° C. by a tubular filmprocess. The stretched film was allowed to pass through a heat treatmentzone set at a predetermined temperature. The resulting film was woundup. The resulting film had a thickness of 12 micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 5.

Example 20

A biaxially stretched film was prepared by the procedure of Example 19,except for using a mixture of 27 parts by weight of the poly(lacticacid) polymer (P1) and 43 parts by weight of the plasticizer (S4) bothof which had been dried at 100° C. under reduced pressure for 6 hours,30 parts by weight of the poly(lactic acid) polymer (P2) which had beendried at 50° C. under reduced pressure for 48 hours or longer, and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting film had a thickness of 12micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 5.

Example 21

A biaxially stretched film was prepared by the procedure of Example 14,except for using a mixture of 75 parts by weight of the poly(lacticacid) polymer (P1), 25 parts by weight of the plasticizer (S8) and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting film had a thickness of 18micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 5.

Example 22

A biaxially stretched film was prepared by the procedure of Example 19,except for using a mixture of 37 parts by weight of the poly(lacticacid) polymer (P1) and 28 parts by weight of the plasticizer (S4) bothof which had been dried at 100° C. under reduced pressure for 6 hours,35 parts by weight of the poly(lactic acid) polymer (P2) which had beendried at 50° C. under reduced pressure for 48 hours or longer and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting film had a thickness of 18micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 5.

Example 23

A biaxially stretched film was prepared by the procedure of Example 19,except for using a mixture of 45 parts by weight of the poly(lacticacid) polymer (P1) which had been dried at 100° C. under reducedpressure for 6 hours, 20 parts by weight of the plasticizer (S6), 35parts by weight of the poly(lactic acid) polymer (P2) which had beendried at 50° C. under reduced-pressure for 48 hours or longer and 0.3part by weight of a hindered phenol antioxidant “Irganox 1010,” aproduct of Ciba-Geigy Ltd. The resulting film had a thickness of 15micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 6.

Example 24

A biaxially stretched film was prepared by the procedure of Example 19,except for using a mixture of 80 parts by weight of the poly(lacticacid) polymer (P3) which had been dried at 80° C. under reduced pressurefor 12 hours, 20 parts by weight of the plasticizer (S6) and 0.3 part byweight of a hindered phenol antioxidant “Irganox 1010,” a product ofCiba-Geigy Ltd. The resulting film had a thickness of 15 micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 7.

Example 25

A pressed sheet was prepared by the procedure of Example 13 and wassubjected to simultaneous biaxial stretching at a stretching temperatureof 55° C., draw ratios in longitudinal and transverse directions of each3.2 times and an areal ratio of 10 times to yield a biaxially stretchedfilm.

The properties of the biaxially stretched film were determined, and theresults are shown in Table 8.

Comparative Example 6

The poly(lactic acid) polymer (P1) which had been dried at 100° C. underreduced pressure for 12 hours or longer was used alone without theaddition of a plasticizer and was melted in a single-screw extruder at aset melting temperature of 210° C., the melted polymer was introduced toa T-die head having a slit width of 1.0 mm and was extruded into asheet. The sheet was cast on a drum cooled at about 15° C. and therebyyielded an unstretched film. The unstretched film was continuouslystretched 3.5 times in a longitudinal direction between heating rolls at85° C. and was then stretched in a widthwise direction at 80° C. at aset draw ratio of 3.5 times using a tenter stretching apparatus,followed by heat treatment at 140° C. under a tension. The resultingfilm was wound up. The resulting film had a thickness of 20 micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Tables 5, 6, 7 and 8.

Comparative Example 7

The poly(lactic acid) polymer (P1) was dried at 100° C. under reducedpressure for 12 hours or longer. Next, the commercially available etherester plasticizer (S5) was continuously weighed and added to thepoly(lactic acid) polymer (P1) while melting the poly(lactic acid)polymer (P1) at 200° C. in a double-screw extruder so that 25 parts byweight of (S5) was added to 75 parts by weight of (P1). The mixture wasmelted, kneaded and homogenized, and the kneaded product was extrudedinto chips to yield a chip-form composition. The chips were dried at 80°C. under reduced pressure for 24 hours or longer and was subjected tothe following film-formation.

The chips were melted in a single-screw extruder at a set meltingtemperature of 210° C., the melted polymer was introduced to a circulardie, was extruded into a tube, the tube was rapidly cooled using coldwater at about 5° C. The cooled tube was subjected to simultaneousbiaxial stretching at draw ratios of 4 times in a longitudinal directionand 4 times in a widthwise direction under heating at 60° C. by atubular film process. The stretched film was allowed to pass through aheat treatment zone at a predetermined temperature and was wound up. Theresulting film had a thickness of 12 micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Tables 5, 6, 7 and 8.

Comparative Example 8

A mixture of 75 parts by weight of the poly(lactic acid) polymer (P1)which had been dried at 100° C. under reduced pressure for 6 hours, 25parts by weight of the plasticizer (S6), and 0.3 part by weight of ahindered phenol antioxidant “Irganox 1010,” a product of Ciba-GeigyLtd., was melted, kneaded and homogenized in a double-screwkneader-extruder at a cylinder temperature of 200° C., and the kneadedproduct was extruded into chips to yield a chip-form composition.Neither the poly(lactic acid) polymer (P2) exhibiting no crystallinitynor the poly(lactic acid) polymer (P3) exhibiting crystallinity andhaving a melting point lower than 145° C. was added. After drying at 80°C. under reduced pressure for 24 hours or longer, the chips were formedinto a biaxially stretched film by the procedure of Comparative Example7. The resulting film had a thickness of 12 micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Tables 5, 6, 7 and 8.

Comparative Example 9

A mixture of 67 parts by weight of the poly(lactic acid) polymer (P1)which had been dried at 100° C. under reduced pressure for 6 hours, 33parts by weight of the plasticizer (S7) and 0.3 part by weight of ahindered phenol antioxidant “Irganox 1010,” a product of Ciba-GeigyLtd., was melted, kneaded and homogenized in a double-screwkneader-extruder at a cylinder temperature of 200° C., and the kneadedproduct was extruded into chips to yield a chip-form composition.Neither the poly(lactic acid) polymer (P2) exhibiting no crystallinitynor the poly(lactic acid) polymer (P3) exhibiting crystallinity andhaving a melting point lower than 145° C. was added. After drying at 80°C. under reduced pressure for 24 hours or longer, the chips were formedinto a biaxially stretched film by the procedure of Comparative Example7. The resulting film had a thickness of 12 micron.

The properties of the biaxially stretched film were determined, and theresults are shown in Tables 5, 6, 7 and 8.

TABLE 5 Poly (lactic Weight Weight acid) Molecular percentage percentageTrans- polymer// weight of of poly of Weight Weight parency Tensileplasticizer// poly (lactic (lactic acid) plasticizing loss after lossafter retention modulus Heat particle acid) segment in component in dryheat hot-water tempera- of resist- Film Adhe- (weight segment inplasticizer composition treatment treatment ture elasticity ance hazesion percentage) plasticizer [weight %] [weight %] [%] [%] [° C.] [MPa][° C.] [%] [N/cm²] Ex. 14 P1//S2 (57//43) 2000 29 31 0.4 0.5 105 1732155 6.0 0.0 Ex. 15 P1//S3 (72//28) 2000 29 20 0.3 0.4 115 1750 155 1.00.0 Ex. 16 P1//S4 (86//14) 2000 29 10 0.2 0.2 120 1461 155 0.7 0.0 Ex.17 P1//S4 (72//28) 2000 29 20 0.2 0.3 115 980 155 0.9 4.1 Ex. 18P1//S4//F1 2000 29 20 0.2 0.4 — 1055 155 24.2 0.0 (70//28//2) Ex. 19P1/P2//S4 2000 29 20 0.5 0.9 ≧140 550 145 0.7 8.3 (17/55//28) Ex. 20P1/P2//S4 2000 29 31 0.7 1.0 115 355 150 1.2 12.6 (27/30//43) Ex. 21P1//S8 (75//25) 1300 21 20 0.9 1.5 110 840 155 1.0 4.1 Ex. 22 P1/P2//S42000 29 20 0.3 0.5 125 661 155 1.0 6.9 (37/35//28) Com. Ex. 6 P1 (100) —— 0 0.1 0.1 ≧140 3226 160 0.6 0.0 Com. Ex. 7 P1//S5 (75//25) 0 0 25 0.624.2 85 889 155 0.8 7.2 Com. Ex. 8 P1//S6 (75//25) 0 0 25 3.1 6.1 85 627155 0.9 7.9 Com. Ex. 9 P1//S7 (67//33) 1000 20 26 2.9 6.0 80 554 155 1.88.0

TABLE 6 Poly (lactic Molecular Weight Weight acid) weight of percentagepercentage polymer// poly of poly of Weight Weight Trans- Tensileplasticizer// (lactic (lactic acid) plasticizing loss after loss afterparency modulus Heat particle acid) segment in component in dry heathot-water retention of resist- Film Adhe- (weight segment in plasticizercomposition treatment treatment temperature elasticity ance haze sionpercentage) plasticizer [weight %] [weight %] [%] [%] [° C.] [MPa] [°C.] [%] [N/cm²] Ex. 23 P1/P2//S6 0 0 20 1.8 2.1 125 605 155 0.7 9.0(45/35//20) Com. Ex. 6 P1 (100) — — 0 0.1 0.1 ≧140 3226 160 0.6 0.0 Com.Ex. 7 P1//S5 (75//25) 0 0 25 0.6 24.2 85 889 155 0.8 7.2 Com. Ex. 8P1//S6 (75//25) 0 0 25 3.1 6.1 85 627 155 0.9 7.9 Com. Ex. 9 P1//S7(67//33) 1000 20 26 2.9 6.0 80 554 155 1.8 8.0

TABLE 7 Poly (lactic Molecular Weight Weight acid) weight of percentagepercentage polymer// poly of poly of Weight Weight Trans- Tensileplasticizer// (lactic (lactic acid) plasticizing loss after loss afterparency modulus Heat particle acid) segment in component in dry heathot-water retention of resist- Film Adhe- (weight segment in plasticizercomposition treatment treatment temperature elasticity ance haze sionpercentage) plasticizer [weight %] [weight %] [%] [%] [° C.] [MPa] [°C.] [%] [N/cm²] Ex. 24 P3//S6 (80//20) 0 0 20 1.9 1.9 10 89 110 0.9 6.6Com. Ex. 6 P1 (100) — — 0 0.1 0.1 ≧140 3226 160 0.6 0.0 Com. Ex. 7P1//S5 (75//25) 0 0 25 0.6 24.2 85 889 155 0.8 7.2 Com. Ex. 8 P1//S6(75//25) 0 0 25 3.1 6.1 85 627 155 0.9 7.9 Com. Ex. 9 P1//S7 (67//33)1000 20 26 2.9 6.0 80 554 155 1.8 8.0

TABLE 8 Poly (lactic Molecular Weight Weight acid) weight of percentagepercentage polymer// poly of poly of Weight Weight Trans- Tensileplasticizer// (lactic (lactic acid) plasticizing loss after loss afterparency modulus Heat particle acid) segment in component in dry heathot-water retention of resist- Film Adhe- (weight segment in plasticizercomposition treatment treatment temperature elasticity ance haze sionpercentage) plasticizer [weight %] [weight %] [%] [%] [° C.] [MPa] [°C.] [%] [N/cm²] Ex. 25 P2//S4 (7//28) 2000 29 20 2.5 4.5 ≧140 521 70 0.97.1 Com. Ex. 6 P1 (100) — — 0 0.1 0.1 ≧140 3226 160 0.6 0.0 Com. Ex. 7P1//S5 (75//25) 0 0 25 0.6 24.2 85 889 155 0.8 7.2 Com. Ex. 8 P1//S6(75//25) 0 0 25 3.1 6.1 85 627 155 0.9 7.9 Com. Ex. 9 P1//S7 (67//33)1000 20 26 2.9 6.0 80 554 155 1.8 8.0

Example 26

Potato salad was placed in a glass bowl, and an opening of the bowl wascovered by the film according to Example 19 as a wrap film. The wrapfilm was in intimate contact with the opening of the bowl along thecurve thereof and fully covered and sealed the opening of the bowl evenafter the hand was left, showing good handleability.

The wrap film kept its intimate contact even after storing in arefrigerator for one week as it was and showed no surface tackiness.

Cold rice was placed in a bowl, was covered by the above-mentioned filmand was heated in a microwave oven. The film was then observed to findthat the film did not break, was not fused to the bowl, did not changein its transparency as compared with that before heating and did notshow surface tackiness.

Example 27

A total of five high of four bags each containing 25 kg of poly(lacticacid) chips were piled up on a wood pallet. The film according toExample 22 as a pallet stretch film was wound around the piled paperbags. The film sufficiently elongated and deformed well along the shapeof the piled paper bags. The film did not spontaneously unwind afterwinding and showed sufficient adhesion, indicating good handleability.

Example 28

A film was prepared by the procedure of Example 18, except for changingthe thickness to 25 μm. The film was placed in agricultural land inShiga Prefecture in Japan in the same manner as in a commerciallyavailable agricultural mulch film. This film showed appropriateflexibility and could be easily placed along the shape of the soilwithout portions out of the soil. The film did not break and did notleft wrinkled even when the film-was trampled during the placingprocedure.

The film showed substantially equal flexibility to that immediatelyafter placing and did not show breakage or surface tackiness even afterleft stand for three months. After left stand for nine months, the filmpartially broken and scattered into pieces as a result of decomposition.The soil was tilled together with the film using a tiller. The film waseasily pulverized and turned up into the soil.

Example 29

A pressure-sensitive adhesive label was prepared by dissolving 5 partsby weight of naturally occurring rubber and 1 part by weight ofnaturally occurring rosin in 94 parts by weight of toluene, applying thesolution to the film according to Example 18 as a base film and dryingthe applied solution to form a pressure-sensitive adhesive layer 15 μmthick thereon. A paper label on an empty beer bottle was fully removed,and the surface of the beer bottle was sufficiently washed and dried.Then the above-prepared label was applied to a surface of the beerbottle to find that the label itself finely followed the curve of thebeer bottle and came in intimate contact therewith. In this procedure,the label was applied so that part thereof covered the shoulders of thebeer bottle. The label showed appropriate extensibility, finely followedthe curve of the beer bottle and came in intimate contact therewith.

Example 30

A pressure-sensitive adhesive tape was prepared in the following manner.A solution was prepared by dissolving 5 parts by weight of naturallyoccurring rubber and 1 part by weight of naturally occurring rosin in 94parts by weight of toluene. The solution was applied to the filmaccording to Example 16 as a base film and was dried to form apressure-sensitive adhesive layer 15 μm thick thereon. A release filmcomprising a poly(vinyl alcohol) (PVA) film was then applied to thesurface of the pressure-sensitive adhesive layer under pressure andthereby yielded the pressure-sensitive adhesive tape. Packing wascarried out using the above-prepared tape to find that the tape showedsufficient extensibility, finely followed the curve of an article to bepackaged and showed satisfactory handleability.

Example 31

A trash bag was prepared by forming raw materials having the samecomposition as in Example 18 into a film 20 μm thick by blown filmextrusion, and cutting and heat-sealing the resulting film. This trashbag was used for refuse disposal instead of a commercially availablepolyethylene trash bag to find that the trash bag showed appropriateflexibility and masking property and could be handled satisfactorilywithout break to form a hole or tearing in a bending portion.

Example 32

A film was prepared by the procedure of Example 16, except for settingthe temperature in heat treatment after stretching at 60° C. and settingthe thickness of the film at 18 μm. A commercially available disposablelunchbox was packaged by heat-sealing three sides of the above-preparedfilm. The lunchbox comprised a lid member made of a biaxially stretchedpolystyrene and a body member made of a talc-containing polypropylene(PP). The packaged lunchbox was subjected to heat treatment in a hot-airoven at an inside temperature of 100° C. for about 1 minute. As aresult, the film deformed in accordance with the shape of the lunchboxdue to heat shrinkage to thereby package the entire lunchbox withoutirregular shrinkage or surface waviness of the film. The film neitherbroke nor fused to the lunchbox. In addition, the film showed equivalenttransparency to that before heat treatment and did not show surfacetackiness.

INDUSTRIAL APPLICABILITY

The poly(lactic acid) polymer compositions exhibit satisfactoryflexibility and show very small amount of the evaporation, migration andextraction (bleedout) of plasticizers and losing transparency uponheating in use as formed plastics, which properties have not yet beenachieved by conventional technologies. The poly(lactic acid) polymercompositions are usable in a wide variety of applications, for example,as formed plastics such as packaging wrap films and other films.

In addition, the poly(lactic acid) polymer compositions exhibitbiodegradability in natural environment higher than conventionalplastics and can be relatively easily-degraded in natural environmentafter use. The poly(lactic acid) polymer compositions are very usefulfor solving environmental issues caused by plastic wastes.

1. A film formed from a formed plastic comprising a poly(lactic acid)polymer composition comprising a mixture of a) a poly(lactic acid)polymer having a weight-average molecular weight M_(w) of 50,000 or moreexhibiting crystallinity, b) a poly(lactic acid) polymer having aweight-average molecular weight M_(w) of 50,000 or more exhibiting nocrystallinity and c) plasticizer comprising at least one poly(lacticacid) component with a number average molecular weight M_(n) of 1200 ormore per molecule and chemically bound to a polyester component, andwherein the film has a tensile modulus of elasticity of 100 to 1500 MPaand has an adhesion of 5 to 30 N/cm².
 2. A film formed from a formedplastic comprising a poly(lactic acid) polymer composition comprising amixture of a) a poly(lactic acid) polymer having a weight-averagemolecular weight M_(w) of 50,000 or more exhibiting crystallinity, b) apoly(lactic acid) polymer having a weight-average molecular weight M_(w)of 50,000 or more exhibiting no crystallinity, and c) a plasticizercomprising a polyester component and containing no poly(lactic acid)segment component with a number average molecular weight M_(n) of 1200or more, and wherein the film has a tensile modulus of elasticity of 100to 1500 MPa and has an adhesion of 5 to 30 N/cm².
 3. A film formed froma formed plastic comprising poly(lactic acid) polymer compositioncomprising a mixture of a) a poly(lactic acid) polymer having aweight-average molecular weight M_(w) of 50,000 or more exhibitingcrystallinity and having a melting point lower than 145° C., b) apoly(lactic acid) polymer having a weight-average molecular weight M_(w)of 50,000 or more exhibiting no crystallinity and c) a plasticizercomprising a polyester component and containing no poly(lactic acid)component with a number average molecular weight M_(n) of 1200 or more,and wherein the film has a tensile modulus of elasticity of 100 to 1500MPa and has an adhesion of 5 to 30 N/cm².
 4. The film according to claim1, in which the plasticizer further comprises at least one poly(lacticacid) component having a number average molecular weight M_(n) of 1500or more per molecule.
 5. The film according to any one of claims 1, 2and 3, in which the weight percentage of the poly(lactic acid) componentof the plasticizer is less than 50 percent by weight of the total of theplasticizer.
 6. The film according to any one of claims 1, 2 and 3, inwhich the weight percentage of a plasticizing component except thepoly(lactic acid) component of the plasticizer is 5 percent by weight ormore and 30 percent by weight or less of the total of the composition.7. The film according to any one of claims 1, 2 and 3, in which thecomposition has been stretched 1.1 times or more in at least one axialdirection.
 8. The film according to any one of claims 1, 2 and 3, inwhich the film has a heat resistance of 120° C. to 230° C.
 9. The filmaccording to any one of claims 1, 2 and 3, in which the film has a filmhaze of 0.2 to 5 percent.
 10. The film according to any one of claims 1,2 and 3, in which the film is selected from a packaging wrap film, astretch film, an agricultural film, a film for label, a film for tape, afilm for protecting a base material and a film for bag.
 11. The filmaccording to claim 1, wherein heat of fusion of crystal (ΔH_(po))derived from the poly(lactic acid) component of the plasticizer is 3.0J/g or more.